1. Field of the Invention
This invention relates generally to oilfield wellbores and more particularly to wellbore systems and methods for the use of flowable devices in such wellbores.
2. Background of the Art
Hydrocarbons, such as oil and gas, are trapped in subsurface formations. Hydrocarbon-bearing formations are usually referred to as the producing zones or oil and gas reservoirs or xe2x80x9creservoirs.xe2x80x9d To obtain hydrocarbons from such formations, wellbores or boreholes are drilled from a surface location or xe2x80x9cwell sitexe2x80x9d on land or offshore into one or more such reservoirs. A wellbore is usually formed by drilling a borehole of a desired diameter or size by a drill bit conveyed from a rig at the well site. The drill string includes a hollow tubing attached to a drilling assembly at its bottom end. The drilling assembly (also referred to herein as the xe2x80x9cbottomhole assemblyxe2x80x9d or xe2x80x9cBHAxe2x80x9d) includes the drill bit for drilling the wellbore and a number of sensors for determining a variety of subsurface or downhole parameters. The tubing usually is a continuous pipe made by joining relatively small sections (each section being 30-40 feet long) of rigid metallic pipe (commonly referred to as the xe2x80x9cdrill pipexe2x80x9d) or a relatively flexible but continuous tubing on a reel (commonly referred to as the xe2x80x9ccoiled-tubingxe2x80x9d). When coiled tubing is used, the drill bit is rotated by a drilling motor in the drilling assembly. Mud motors are most commonly utilized as drilling motors. When a drill pipe is used as the tubing, the drill bit is rotated by rotating the drill pipe at the surface and/or by the mud motor. During drilling of a wellbore, drilling fluid (commonly referred to as the xe2x80x9cmudxe2x80x9d) is supplied under pressure from a source thereof at the surface through the drilling tubing. The mud passes through the drilling assembly, rotates the drilling motor, if used, and discharges at the drill bit bottom. The mud discharged at the drill bit bottom returns to the surface via the spacing between the drill string and the wellbore (also referred herein as the xe2x80x9cannulusxe2x80x9d) carrying the rock pieces (referred to in the art as the xe2x80x9ccuttingsxe2x80x9d) therewith.
Most of the currently utilized drilling assemblies include a variety of devices and sensors to monitor and control the drilling process and to obtain valuable information about the rock, wellbore conditions, and the matrix surrounding the drilling assembly. The devices and sensors used in a particular drilling assembly depend upon the specific requirements of the well being drilled. Such devices include mud motors, adjustable stabilizers to provide lateral stability to the drilling assembly, adjustable bends, adjustable force application devices to maintain and to alter the drilling direction, and thrusters to apply desired amount of force on the drill bit. The drilling assembly may include sensors for determining (a) drilling parameters, such as the fluid flow rate, rotational speed (r.p.m.) of the drill bit and/or mud motor, the weight on bit (xe2x80x9cWOBxe2x80x9d), and torque of the bit; (b) borehole parameters, such as temperature, pressure, hole size and shape, and chemical and physical properties of the circulating fluid, inclination, azimuth, etc., (c) drilling assembly parameters, such as differential pressure across the mud motor or BHA, vibration, bending, stick-slip, whirl; and (d) formation parameters, such as formation resistivity, dielectric constant, porosity, density, permeability, acoustic velocity, natural gamma ray, formation pressure, fluid mobility, fluid composition, and composition of the rock matrix.
During drilling, there is ongoing need to adjust the various devices in the drill string. Frequently, signals and data are transmitted from surface control units to the drilling assembly. Data and the sensor results from the drilling assembly are communicated to the surface. Commonly utilized telemetry systems, such as mud pulse telemetry and acoustic telemetry systems, are relatively low data rate transfer systems. Consequently, large amounts of downhole measured and computed information about the various above-noted parameters is stored in memory in the drilling assembly for later use. Also, relatively few instructions and data can be transmitted from the surface to the drilling assembly during the drilling operations.
After the well has been drilled, the well may be completed, i.e., made ready for production. The completion of the wellbore requires a variety of operations, such as setting a casing, cementing, setting packers, operating flow control devices, and perforating. There is need to send signals and data from the surface during such completion operations and to receive information about certain downhole parameters. This information may be required to monitor status and/or for the operation of devices in the wellbore (xe2x80x9cdownhole devicesxe2x80x9d), to actuate devices to perform a task or operation or to gather data about the subsurface wellbore completion system, information about produced or injected fluids or information about surrounding formation. After the well has started to produce, there is a continuous need to take measurements of various downhole parameters and to transmit downhole generated signals and data to the surface and to receive downhole information transmitted from the surface.
The present invention provides systems and methods wherein discrete flowable devices are utilized to communicate surface-generated information (signals and data) to downhole devices, measure and record downhole parameters of interest, and retrieve from downhole devices, and to make measurements relating to one or more parameters of interest relating to the wellbore systems.
This invention provides a method of utilizing flowable devices to communicate between surface and downhole instruments and to measure downhole parameters of interest. In one method, one or more flowable devices are introduced into fluid flowing in the wellbore. The flowable device is a data carrier, which may be a memory device, a measurement device that can make one or more measurements of a parameter of interest, such as temperature, pressure and flow rate, and a device with a chemical or biological base that provides some useful information about a downhole parameter or a device that can transfer power to another device.
In one aspect of the invention, memory-type flowable devices are sent downhole wherein a device in the wellbore reads stored information from the flowable devices and/or writes information on the flowable device. If the flowable device is a measurement device, it takes the measurement, such as temperature, pressure, flow rate, etc., at one or more locations in the wellbore. The flowable devices flow back to the surface with the fluid, where they are retrieved. The data in the flowable devices and/or the measurement information obtained by the flowable devices is retrieved for use and analysis.
During drilling of a wellbore, the flowable devices may be introduced into the drilling fluid pumped into the drill string. A data exchange device in the drill string reads information from the flowable devices and/or writes information on the flowable devices. An inductive coupling device may be utilized for reading information from or writing information on the flowable devices. A downhole controller controls the information flow between the flowable device and other downhole devices and sensors. The flowable devices return to the surface with the circulating drilling fluid and are retrieved. Each flowable device may be assigned an address for identification. Redundant devices may be utilized.
In a production well, the flowable devices may be pumped downhole via a tubing that runs from a surface location to a desired depth in the wellbore and then returns to the surface. A U-shaped tubing may be utilized for this purpose. The flowable devices may also be carried downhole via a single tubing or stored in a container or magazine located or placed at a suitable location downhole, from which location the flowable devices are released into the flow of the produced fluid, which carries the flowable devices to the surface. The release or disposal from the magazine may be done periodically, upon command, or upon the occurrence of one or more events. The magazine may be recharged by intervention into the wellbore. The tubing that carries the flowable devices may be specifically made to convey the flowable devices or it may be a hydraulic line with additional functionality. The flowable devices may retrieve information from downhole devices and/or make measurements along the wellbore. A plurality of flowable devices may be present in a wellbore at any given time, some of which may be designed to communicate with other flowable device or other downhole device, thereby providing a communication network in the wellbore. The flowable devices may be intentionally implanted in the wellbore wall to form a communication link or network in the wellbore. A device in the wellbore reads the information carried by the flowable devices and provides such information to a downhole controller for use. The information sent downhole may contain commands for the downhole controller to perform a particular operation, such as operating a device. The downhole controller may also send information back to the surface by writing information on the flowable devices. This may be information from a downhole system or confirmation of the receipt of the information from surface.
Examples of the more important features of the invention have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art maybe appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.